An earth-boring bit of the type concerned herein has a bit body with at least one bearing pin, normally three, and a cone rotatably mounted to each bearing pin. Each cone has cutting elements for disintegrating the earth formation as the bit body rotates. The bearing spaces between the cavity of the cone and the bearing pin are filled with a lubricant. A seal is located near the mouth of the cone cavity for sealing lubricant from drilling fluid.
In drilling service, debris, whether it originates from the bearing or the bore hole, might find its way to the seal and cause wear. One type of seal comprises an elastomeric member with an inner diameter in sliding engagement with the bearing pin and an outer diameter that is normally in static engagement with the cone. This type of seal forms a nip area with the bearing pin and invites debris to accumulate near and migrate into the sealing interface. The accumulated debris causes wear and leakage.
Another type of seal employs primary metal-to-metal face seals energized by an elastomeric ring. One type of seal assembly employs a secondary elastomeric seal exterior of the energizer ring to protect the primary seal. The secondary seal takes up precious space, and the assembly requires pressure compensation for the space between the two seals.
Other designs use an elastomeric ring that has a more wear-resistant elastomeric layer upon the inner diameter. The more wear-resistant layer may comprise a different elastomer, or it may be made up of a wear-resistant fabric.